More elegant way of solving exact equations
Merge pull request #1955 from Manoj-Kumar-S/speed

More elegant way of solving exact equations
Implement rewrite as Piecewise for Abs, sign and Heaviside (issue 3478)
Cleanup _eval_rewrite_as_Heaviside() method for Abs
Revert back some unnecessary changes in test_delta_functions.py
More explicit checks for cases real=True is not set